This invention relates generally to expansion joint seals of the type used for sealing an expansion joint space or gap against the intrusion of dirty, water and other debris as for example might be encountered by expansion joints employed in roadway construction. More specifically, the present invention relates to an elastomeric expansion seal that may be employed in a joint assembly having elongated, metal edge members installed on either side of the gap as defined by a pair of structural members such as concrete slabs wherein the seal is connected between said edge members.
One problem encountered with many available expansion joint seals is that the retaining or mounting bead portions become dislodged from one of the edge members over part or all of the longitudinal lengths of the joint with the result that the seal no longer remains watertight and thus, ceases to perform one of the principal functions for which it was provided.
There have been various proposals for design of the seal mounting beads and other approaches to the design of expansion joint seals in general which have had the objective of minimizing the possibility of failure of the joint by dislodging of the seal from the frame or edge members of the assembly. In regard to expansion seals having mounting beads along the longitudinal edges thereof for mounting in a corresponding cavity of the edge members, a number of specific problems have been encountered. It has been found very difficult in the prior art to form metal edge members having a cavity therein of predetermined cross section which includes any degree of high tolerance along the entire extruded length of such an edge member. For example in extruding a metal edge member with a cavity therein on the order of 16 feet in longitudinal length, as might be utilized in a road joint, it has been found that the extrusion process fails to maintain uniformity in the cross sectional dimensions of the cavity along the entire longitudinal length thereof. On the other hand, it has been found possible in the prior art to maintain a relatively high degree of tolerances with respect to the outer surfaces cross sectional dimensions of an extruded mounting or retaining bead of an expansion seal. Necessarily, the resultant differences in uniformity between the aforesaid seal beads and associated cavities result in the possibility of the bead being more easily dislodged from the edge member.
Another problem encountered in the prior art results from the necessity of reducing the size of the bead to permit its insertion into the cavity of an edge member. A common technique for permitting the reduction in size of the bead is to make it hollow, thereby permitting the bead to be compressed for reception into the retaining cavity of an edge member. Unfortunately, it has been found that such prior art hollow beads operate in reverse in that being subject to compression they can be easily pulled out of the edge member cavity under various conditions, such as water intrusion and freezing.